The O-ring is to keep debris away from the bearing on the throttle shaft. Not to seal out an air leak.
The TPS is probably bad.
There is a good portion of people who've found a loophole in returning electronic parts. Clean up the broken old part, put it in the box of the new one and return it to the store claiming it wasn't the correct part. Next guy in line gets a broken used part. Yay.
Don't "think outside the box".
There is no box.